Remote control sound record reproducing system



REMOTE CONTROL SOUND RECORD REPRODUCING SYSTEM Fil d July 29, 1940 4 Sheets-Sheet l QM A 3' 6 LM w 5 wow m Jm m 0A a HM WWW m. Q v 5% ma m a A RA H Fm m K 5/ v m H wow A m8 9% 08 April 22, 1941. F. A. HADEL ETAL 2,238,976

REMOTE CONTROL SOUND RECORD HEPRODUCING SYSTEM FiledJ uly 29, 1940 4 Sheets-Sheet 2 /Nl/EN7'OR-5 F4 50 A. HA DEL REA v. THO/MP6 ON I I I I I I I I l. I I

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REMO TE CONTROL SOUPdD RECORD REPRODUCING SYSTEM Filed July 29, 1940 4 Sheets-Sheet 4 2m R0 mAM N W M m A Trek V556 Patented Apr. 22, 1941 REMOTE CONTROL SOUND RECORD REPRODUCING SYSTEM Fred A. Hadel and Rea J. Thompson, Los Angeles,

Calif., assignors of one-half to Carl F. Huehotter, Los Angeles, Calif.

Application July 29, 1940, Serial No. 348,250

21 Claims.

, This invention relates to a multiple unit sound record reproducing system with a remote central control. It is particularly adapted to the remote control by an operator of a plurality of separated music record reproducing stations, herein referred to as location stations, located in cafes,

amusement resorts, and similar public gathering places.

In a system of this kind to which this invention is particularly adapted, a plurality of receiving cabinets are located respectively at the business-places of the systems subscribers and are connected to a common central control station over leased wires in cables of the local telephone utility. Each cabinet is equipped with a coin-receiving signalling means by which the operator at the central control station is notified that a customer wishes to avail himself of the playing service, with means for telephonic communication with the operator by which the customer arranges with the operator for the record selections to be played, and with means for receiving from the central station and transforming into sound the recorded music. The central station is equipped with indicators to notify the location station and the central control station, will transmit coin drop signals and vocal inv formatory signals from a location station to the operator of service requests, with means for telephonic communication with the customers, with means for playing records and transmitting their recorded sounds to the subscriber cabinets, and with a collection of records to be played.

One object of this invention is to provide a system of this character which will utilize relatively simple and inexpensive equipment of high eiliciency. Another object is to eliminate inter ference between the cable wires of the system and between these wires and the other wires in the same cable which connect telephone subscribers with the central station of the telephone utility, and particularly to eliminate interference arising from the transmission of the coin signals of therecord playing system.

Another object is to provide a hook-up in-su ch a system which by means of novel electrical connections and switch mechanism will be adapted for indicative signalling, for informative communication and for record transmission in different sequences according to varying circumstances created by the customers conduct, and with greatest convenience to-the customer and with a minimum of acts and attention by the operator.

Another object is to reproduce a sound record with a high degree of fidelity in a system of the type described.

Another object is to provide a system which, while requiring but a single circuit between each central control station and will also transmit vocal informatory signals and reproduced record signals from the central control station to the lo-- cation station without interference, cross signalling or confusion to customer or operator when at proper levels of sound intensity. g

Another object is to provide a central control station hookup which will provide adequate and efficient control of a plurality of location stations and do it with a minimum of equipment.

Still another objectis to provide that all types of signals shall, from their point of origin to, their point of final reception, be at proper intensity levels'both from the standpoint of the receiving person or persons or the receiving instrument, and from the standpoint of the proper functioning of the transmitting equipment and particularly of the telephone cables connecting the location stations with the central control station.

Other objects and advantages of the invention will appear as the invention becomes understood from the specification and drawings disclosing one embodiment of the invention and from a reading of the claims in which the subject matter of the invention is defined.

In the drawings, Fig. 1 is a schematic showing 6f the devices of a system embodying my invention, and of their electrical relationship.

Fig. 2 is a wiring diagram showing the nature and arrangement of the electrical elements in the several devices of a location station of the system and of one of the units of the central station, and the electrical connections within the devices, between the devices of the location station, between the devices of the central station, and between the location station and central station.

Fig. 3 is a front elevational view of the upper portion of one section of the central station cabinet.

Fig. 4 is a view in front elevation of one of the 'coin signal-receiving instruments at the central station.

Fig. 5 is a view in rear elevation of the same. Fig. 6 is a view similar to Fig. 5, showing the parts of the instrument in a different operative position.

Fig. 9 is a wiring diagram of the electrical connections of the coin signal-receiving instrument. Fig. 10 is a wiring diagram similar to that shown in Fig. 2, but of a modified form of the invention.

In order to describe the invention in a practical workable embodiment, values are given in the following description to the characteristics of the several devices and instruments of the system, but it will be understood that the invention is not necessarily limited to these specific values.

Referring to Fig. 1, everything to the right of the line 11-21: indicates schematically the devices, instruments, and electrical connections at an operators central control station CCS. To the left of the line :ca: and immediately adjacent thereto is schematically indicated bteween the dash lines yy and zz a telephone cable TC. Also, to the left of the line :c:c are schematically indicated by rectangular symbols location stations L to L inclusive, the several devices, instruments, and electrical connections at each of these stations being assembled in a suitable cabinet.

Conductor connections indicated as a whole by the numeral II lead from the station L into the telephone cable TC and thence to the control station 'CCS. These conductor connections H preferably comprise two wire conductors provid ing an all-wire circuit rather than a single wire conductor with a ground return. Similar conductor connections l2 to 22, inclusive, from location cabinets L to L respectively, are indicated by similarly numbered lines on Fig, 1, and lead to the central control station 008 through the telephone cable TC. It will be understood that these otherconductor connections may lead to the central control station through other telephone cables, depending upon the geographical position of the location stations with reference to each other and to the control station.

With the exception of a monitor speaker MS (see Fig. 1), all of the devices and instruments of the central control station CCS are assembled on a cabinet, the upper portion of a section CS of which is shown in Fig. 3. The central control ment of which a plurality are used in the sysstation cabinet has a plurality of these sections CS of three control units each. These control units will be hereinafter identified on the drawings and will be referred to in the following description by the letter C with the addition of a numerical suffix when reference is made to one or more of the units in particular.

Preferably, a cabinet is made up of four to eight/sections bolted or otherwise secured together along their end faces 26, all of the sections CS being connected to one monitor speaker in a manner to be hereinafter described. In the embodiment of the invention shown and described herein, there are four sections CS comprising the cabinet at the central control station CCS.

Each cabinet has a vertical switchboard panel 21 (see Fig. 3) and three horizontal decks dis posed at the base of the panel 21. An uppermost deck 28 is shown in Fig. 3, its upper horizontal surface 29 extending forwardly from the lower edge of the panel 21. A middle deck and lowermost deck (not shown) are disposed below the deck 28 in stepped relationship thereto, the middle deck projecting forwardly from the deck 28, the lowermost deck in turn projecting forwardly from the middle deck. Each of these decks is similarly equipped with a turntable 30 and a pick-up 3|, which together constitute a record reproducing unit PI.

tem, a designating numeral or letter or letters will be used for signifying any one of such parts, elements, or members without particularizatlon, and the same numeral or letter designation will be used with a small letter or numeral suflix to make reference to a particular one of the group.

The switchboard panel 21 has mounted upon its front face in the positions shown in Fig. 3 coin indicator dials 32a, 32b,and 320, respectively associated pointers 33a, 33b, and 330, coin indicator lamps 34a, 34b, and 340, talk-'listen-play switch handles and dials'35a, 35b, and 350, volume control switch handles and dials 36a, 35b, and 360, a volume indicator VI, a volume indicator switch handle 31, a volume control handle 38, a microphone MI and speaker O. In addition, only one of the sections CS of each battery of sections under unitary control is equipped with a monitor speaker switch handle and dial 39.

Coin indicating devices of which the dials 32 and pointers 33 are parts are each constructed as shown in Figs. 4 to 8, are mounted three on a back of each one of the panels 21, and are designated on the schematic diagramof Fig. 1 as I to I inclusive. spectively of these coin indicating devices. Talkl-isten-play switches, associated respectively with the talk-listen-play switch handles and dials 35 are mounted three on a back of each one of the panels 21 and are shown schematically on Fig. 1, and there designated TLPS to TLPS, inclusive. The volume control handles and dials 36 are associated with volume controls mounted three on the back of each one of the panels 21 and schematically shown and designated on Fig. 1 as V0 to V0 inclusive. These volume controls are associated respectively with triode low-distortion line amplifiers SA to SA schematically shown on Fig. 1 and conveniently mounted three on each of the control unit sections CS in amanner not shown. Pentode power amplifiers RA to RA, inclusive, are also mounted at some convenient location, three upon each of the cabinet sections CS, and are schematically shown and so designated on Fig. 1. These amplifiers may with proper design be of the push-pull triode type.

The amplifiers RA and SA, the volume controls VC, and the talk-listen-play switches TLPS are symbolically represented in Fig. 1 to show the group character of their relationship with each other and with the other devices of the system, but for a detailed showing of the electrical connections between these devices and between them and the otherdevices of the system, reference must be had to other figures of the drawings and to later portions of this description.

Four volume indicators VI, sub-identified as VI to VI, inclusive, are schematically shown in Fig. 1, Four volume indicator switch handles 31, one of which is shown in Fig. 3, operate respectively four volume indicator selector switches mounted one on the back of each panel 21, and are designated on Fig. 1 as VIS to V18 inclusive. Four volume control handles 38 operate respectively four volume controls mounted one on the back of each of the panels 21, and are designated as VCJO to V00 inclusive, on Fig. 1. The monitor speaker switch handle 39, which is mounted on only one of the panels 21, operates a monitor speaker switch on the rear of that panel. This switch is shown and designated as MSS on Fig. 1. By this switch any one of the three units C of any con- The lamps 34 are also parts retrol section CS may be connected to a monitor speaker amplifier MSA and a monitor speaker MS. The amplifier MSA is preferably mounted on the control cabinet section of that panel 21 on which is mounted the switch MSS. A record reproducing unit PI forms a part of each control unit C. These record producing units P1 are shown on Fig. 1 and are designated P1 to P1 inclusive.

Power supply units PSC, shown and sub-designated as PSC to PSC, inclusive, on Fig, 1, are conveniently mounted one in each control section CS of the control cabinet CCS, and each supplies electric current to all three units C of its associated section CS. One power supply unit PSC supplies current to the amplifier MSA.

As above pointed out, all of the sections CS of the cabinet CCS under the control of one operator are considered as a control station, which station comprises all of the devices and electrical connections shown to the right of the line :r-a: on Fig. 1. The monitor speaker switch MSS, and monitor speaker amplifier MSA mounted on one of the cabinet control sections CS, and the monitor speaker MS which is not mounted on the cabinet but, at a nearby point within the hearing of the operator, are common to all control units of the control station CCS. While the designating reference letters 008 are used herein to refer both to the central control station as to functional entity and the central control station cabinet as a physical article, it will be understood that the monitor speaker MS is preferably physically mounted independently of the cabinet, and other devices of the central control station may i also, if desired; be physically mounted elsewhere,

although functionally related to the devices mounted on the cabinet in the manner herein described.

vEach section CS comprises three units C, each of which includes the devices and wiring connections which are schematically shown within one of the areas boundedby dash lines and designated on the drawings as C to C inclusive. The designating character C will be used to refer to a control unit as a functional entity and as comprising all of the devices schematically enclosed within any one of the rectangles designated on the drawings as C to C inclusive:

Lines 40 on Fig. 1 represent the conductor connections respectively by which each of the power supply units PSC furnishes current to the amplifiers SA and RA of the three units C of a control section CS which is associated with that power supply unit. Line 40a represents ,the conductor connections, from PSC to the monitor speaker amplifier MSA. Conductor connections H to 22 lead from the cable TC into the control units C to C, respectively. Each talk-.listen-play associated coin indicating device I by means of conductor connections 49.

The three amplifiers SA of each control section CS are connected to an associated volume indi-.

- tor speaker switch MSS is connected tothe twelve switch TLPS is electrically connected to both an associated amplifier SA and an associated amplifier RA. The three talk-listen-play switches TLPS of each control section CS are connected for talking purposes by conductor connections 43 to an associated microphone MI. The three talklisten-play switches TLPS of each control section CS are'also connected by conductor connections 46 to an associated volume control VCO, which is in turn connected by conductor connections 41 to an associated speaker O for listening purposes,

Each talk-listen-play switch TLPS is connected amplifiers SA to SA, inclusive, by conductor connections 51. The numeral 59 designates the conductor connections between the monitor speaker selector switch MSS and the monitor speaker amplifier MSA, and 59a the conductor connections between this amplifier and the speaker MS.

In Fig. 2 is shown a complete wiring diagram of a location station L, of one unit C of the central control station CCS, of the telephone cable connections TC between these stations, and of those devices of a control section CS which are common to its' three control units C; i. e.,.the section power supply unit PSC, section microphone MI, section speaker O with its volume control VCO, and section volume control indicator V1 with its switch VIS.

To the left of the line :c-a: is shown the wiring diagram of the location station L and the telephone cable TC, the latter being shown between the line :c:r and the short dash line y-y. To the right of the line a::c are shown the devices individual to a piayer control unit C and a control section CS.

Considering first the devices of a location station L, the parts, devices, and electrical connections of a triode pre-amplifier MA are shown by standard symbols within a space enclosed by dash lines and designated MA. Within similarly enclosed and designated spaces are shown a power supply unit PS and a triode low-distortion power amplifier FA. The amplifier FA is provided with a 1000-cycle dipper and band rejector filter DF, connected as shown, A microphone M, a coin drop D, a high fidelity speaker HF, a matching transformer MT, a double-pole double-throw push button switch DPP, and a double-pole doublethrow relay switch DPR are shown by standard symbols.

At the central control station, to the right of dash line :c-:r are shown respectively within spaces enclosed by dash lines the pentode power amplifier RA, the power supply unit PSC, the triode line amplifier SA, the talk-listen-play switch TLPS, and the coin indicator 1. The amplifier RA is provided with a IOU-cycle dipper filter E-QD connected as shown. The amplifier SA is provided with a 50-cycle cutoff filter EQC connected as shown. The microphone MI, the speaker O with its associated. matching transformer MTO and volume control VCO, the volume indicator switch VIS, volume indicator VI, and record reproducing unit P1 are shown by appropriate symbols,

The double-pole double-throw push button DPP comprises a manually operated push button 4|, movable switch leaves 50 and 56, and contacts 52, 53, 55, and 58. The leaves 50 and 56 are normally electrically connected to contacts 53 and to its associated record reproducing unit PI by means of conductor connections 48. Each talklisten-play switch TLPS' is also connected to an 55. Upon inward movement of the push button ll, the leaves 50 and 56 break connection with these contacts and engage respectively contacts 52 and 58.

The double-pole double-throw relay switch DPR comprises a solenoid coil 10, an armature rod H, movable switch leaves BI and 65 secured at their movable ends to the armature rod H,

and contacts 60, 62, 63, and 64. Energization of the solenoid coil causes the armature rod H to move the switch leaves 6| and 65 from their normal position in which they engage the contacts 62 and 64 to a position in which they engage respectively the contacts 60 and 63.

The contacts 52 and of the double-pole double-throw push button switch DPP are connected by conductors 13 and 12 respectively to the terminals of the transformer coil '66 of the amplifier MA. The contacts 53 and 55 of this double-pole double-throw switch DPP are connected by conductors 15 and 16 respectively to the terminals of the transformer coil 61 of the amplifier FA. The switch leaves 50 and 56 of this push button switch are connected to contacts 64 and 62 of the double-pole double-throw relay switch DPR by conductors 14 and 11 respectively.

The contacts and 63 of the relay switch DPR are connected to the terminals of the low voltage coil of a transformer III by conductors 82 and 83 respectively, this transformer being connected to a service source of alternating current of standard voltage and frequency, for example, 60 cycles and 110 volts. One terminal of the solenoid coil 10 of the relay switch DPR is connected by a conductor 19 to the coin drop D, the other side. of the circuit of which is connectedby a conductor 69 to one side of a source of current suitable for the operation of the coil 10. The other terminal of the solenoid coil 10 is connected to the other side of this source of current by a conductor 08 along which is interposed,.to provide a safety' load, a lamp 18. The power supply unit PS, which receives its power from a service source of alternating current of standard voltage and frequency through conductors 88, is appropriately connected to the amplifier MA by conductors 92, 93, and 94, and

to the amplifier FA by conductors 95, 96, 91, 98, 99, and I00. It also supplies current through the conductor 9| and a ground return to the field coil 90 of the high fidelity speaker HF.

The amplifier MA is connected to the microphone M by means of the conductor 86 and ground return 81. The amplifier FA is connected to the matching transformer MT of the high fidel .ity speaker HF by conductors 89. The switch leaves 5| and of the relay switch DP-R are connected to conductors 84 and 85 which lead into the cable TC and thence to the control unit C.

The conductors B4 and 85 are connected to the terminals of a transformer coil I50 of the pentode power amplifier RA through resistances I52 and I5I which provide an impedance suffioient to give a total impedance of approximately 600 ohms between the coil I50 and the switch leaves 6| and 65 including a coil I55 of the triode line amplifier SA. The conductors 84 and 85 are also connected to conductors I53 and I54 respectively, which are in turn connected to the terminals of the transformer coil I55.

The several devices of the amplifiersRA and SA are supplied with current of appropriate characteristics from the power supply unit PSC by conductors I80 in a hook-up of standard arrangement, as indicated on Fig. 2. This power supply unit PS0 is similarly connected to the other two amplifiers RA and the other two amplifiers SA of the other two control units 0 of any control section CS as indicated at I8I, I82, I83, I84 and I85. This power supply unit PS0 is connected to a service source of alternating current of standard voltage and frequency, as, for example, 110 volt 60-cycle current, by conductors I88 and I89.

Two cooperating contacts of the three-unit section volume indicator switch VIS are connected respectively by conductors I96 and I54 to one terminal of the transformer coil I55 of the amplifier SA and by conductors I95 and I53 to the other terminal thereof. The volume indicator VI can be connected across these contacts by the switch arms I90. Two other pairs of cooperating contacts of the volume indicator switch VIS are connected to the terminals of the transformer coils corresponding to transformer coil I55 of the other two amplifiers SA of the other two control units C of a control section, by conductors I9I, I92, I93, and I94, and may be connected to the terminals of the volume indicator VI by moving the switch arms I to corresponding positions. The amplifier SA is also connected to the monitor speaker switch M88 and through it to the monitor speaker amplifier MSA and monitor speaker MS through conductors I 53, I95, and I99 on one side, and through conductors I 54, I96, and 200 on the otherside.

The talk-listen-play switch TLPS has three movable contact arms IOI, I02, and I03 which are mechanically united as by being rigidly mounted as radial arms on the same rotatable shaft I04. The arm IOI connects a terminal I 05 alternatively with the stationary contacts I06, I01, and I08 in. the three positions respectively which it is structurally capable of assuming. Similarly, the contact arm I 02 connects a terminal I09 with the stationary contacts I I0, III, and H2, and contact arm I03 connects a terminal II3 with stationary contacts H4, H5, and H6. As indicated by the arrow II1, contact arms IOI, I02, and I03, when moved to the right of the contacts I01, III, and H5, are springurged toward contacts I01, III, and II 5.

The terminal I05 is connected by a conductor II8 to the transformer coil I32 of the amplifier RA. The other end of this coil is grounded at I33. The contact I'06 is connected by conductors H9 and I20 to the coin signal indicator I. The contact I01 is connected through the volume control VCO and matching transformer MTO to the speaker O by conductors I2I, I22, and I23, the volume control VCO being grounded at I34. The conductor I2I is also connected to contracts corresponding to the contacts I01 on the talk-listen-play switches 'I'LPS of the other two control units C of control sections CS by conductor leads I24 and I 25 respectively. The contact I08 is connected to the coin indicator I by conductors I26 and I20.

The terminal I09 is connected to the amplifierfl SA by conductor I2Ia at the high terminal of the volume control V0 in the amplifier SA. The contacts H0 and III are open contacts. The contact H2 is grounded through the resistance I22a. The terminal I I3 is connected to the amplifier SA by conductor I23a which is connected to the grid of the first stage tube in the amplifier SA. The contact H6 is connected by the conductor I24a through an equalizer E to the record reproducing unit PI. The contact H5 15 grounded through conductor I25a. The contact I I4 is connected to the microphone MI by conductor I26a. The microphone MI has a ground return I35. The microphone MI is similarly connected by conductors I21 and I28 to similar contacts of the other two control units.

talk-listen-play switches TLPS of a control section CS.

The pointer operating mechanism of the coin indicator I is electrically powered by current, the sides of the circuitof which are conductor 120 and ground 129. The incandescent lamp 34 of the coin indicator I is supplied with current over conductors 130 and 131 which are connected through the amplifier RA to the power supply unit PSC.

The indicator I is shown in Figs. 4 to 8, inclusive. A vertical frame plate 201 has spotwelded to it a vertical leg 202 of an angle bracket 203 upon a horizontal leg 204 of which is secured an electromagnet 205 by means of a screw 206 having a threaded engagement with a core 201 of the electromaget. Mounted between the bracket leg 204 and the electromagnet 2'05, and held in position by the screw 206, is a U-shaped frame piece 208, which is vertically spacedfrom the electromagnet by a washer 209. An armature arm 210 is pivotally mounted upon the upper end of an upright 211 of the frame piece 208. The armature arm 210 is resiliently urged away from the electromagnet 205 by a spring 212 anchored at its lower end to a lug 213 formed on the upright 211. The armature arm 210 is limited in its downward movement caused by the attractive force of the electromagnet 205 by the upper end of an upright 214 of the frame piece' 208. Since the purpose of the electromagnet is to cause mechanical movement of the am 210, it is a tractive electromagnet.

The vertical frame plate 20! is secured to the cabinet panel 21 by screws 215. The plate 201 is bent perpendicularly at one end along a vertical line to form a flange 216 to which is fastened an angle bracket 21'! having a leg 218 parallel to the base plate 201, the leg 218 being apertured at 219 to form a bearing for a shaft 220. The base plate 201 is similarly apertured to provide a bearing 221 for the other end of the shaft 220. This shaft projects through the cabinet panel 21 and the dial plate 32 which is secured to the panel plate 21, and has rigidly secured. to its projecting end the pointer 33 which also serves as a handle for the operator to return the shaft 220 to the position in which the pointer 33 registers with zero on the dial plate 32.- The shaft 220 is given a resilient torque in the direction indicated by the arrow on Figs. 4 to 6, inclusive, by a coiled spring 222 anchored at one end to the leg 218 of the bracket 211, and secured at the other end to a collar 223 rigidly fastened upon the shaft 220 by a set screw 224.

The shaft 220 also projects beyond the bracket leg 218, and on this projecting end is rigidly mounted a star wheel 225 of the Geneva movement type. The outer end of the armature arm 210 is bent at right angles to form a support 226 for a Geneva movement pawl piece 221 provided at its proper end with a pawl 228 which is perpendicular to the periphery of the star wheel 225 and provided at its lower end with a pawl 229 which forms an acute angle with the ad- .iaicent portion of the periphery of the star wheel 225.

Each of the coin drops D is so constructed that a falling coin makes and immediately thereafter breaks'each of a succession of contacts to a number corresponding to the denomination of the coin. The impulse signals so set up are successively received by the electromagnet 205, causing a succession of downward pulls upon the armature arm 210 and corresponding downward movements of the pawls 228 and 229. As the pawl 229 clears the adjacent one of the teeth 230 of the star wheel 225 which it is contacting, the pawl 228 enters a space between two adjacent teeth 230 and limits the movement of the star wheel 225 under the influence of the torque of the spring 222 by engagement with the tooth 230 at left of the pawl. Upon the deenergization of the magnet 205, prior to the re ception of the next signal impulse, the spring 212 raises the pawl 228 out of engagement with that one of the star wheel teeth 230 which is being spring-urged against it, and at the same time the pawl 229 enters an adjacent registering tooth space limiting the rotation of the star wheel in the well known manner which ischaracteristic of a Geneva movement. In this manner each signal impulse sent from the coin drop moves the pointer 33 one point on the dial, each point indicating the deposit of money to the value of five cents.

When the pointer 33 comes to rest at the end of the succession of signal impulses caused by the deposit of a coin, the operator grasps the pointer 33 and returns it to zero position where it is stopped by engagement of the set-screw 224 with a stop pin 241 mounted on plate 201. The

clearance distance between the pawls 228 and v .229 and the beveled character of the ends of the teeth 230 permit this manually actuated retrograde movement of the star wheel 225 and shaft Upon a bracket 23I spot-welded to the frame plate 201 are insulatedly mounted two switch leaves 232 and 233 which are connected in series between the conductor (see Fig. 2) and the indicator lamp 34. The outer end of the upper leaf 232 is formed with a cam surface 234 by which the leaf 232 is moved upwardly when contacted by the head end of the set-screw 224 as the pointer 33 moves to its zero position. When the leaf 232 is in this upper position, contacts 235 and 235 on the leaves 232 and 233 respectively are separated, normally turning off the lamp 34 when the pointer is at zero position. The first signal impulse received by the electromagnet 205 upon the deposit of a coin of any denomination moves the set-screw 224 in a counter-clockwise direction (see Fig. 7) establishing electrical connection between contacts 235 and 236 and causing illumination of the lamp 34. The lamp remains illuminated during successive movements of the pointer 33, and until the operator returns the pointer 33 to its zero position. Connected in parallel with the coil of the electromagnet 205, is a condenser 240 (see Fig. 9) the capacity of which isso related to the reactive impedance of the coil 205 as to constitute with the coil a band pass filter tuning the electromagnet to operate at the frequency of the alternating current supplied to the system from the electric utility, which is usually 60 cycles. This condenser may be provided by using for the conductor 129 a properly dimensioned grounded shield on the conductor The amplifier MA is so designed that at any,

cation station power supply units PS, to the coin drops D at the location stations through their respective conductors 58 and 69, and to the transformer coils 8| at the location stations through their respective conductors 80 and III, and with power also supplied to the four central control station power units PS0, and with the talk-listenplay switches 'I'LPS in the leftward of their three positions, as shown in full lines in Fig. 2, the system is in readiness for operation. A coin, which we shall take for illustration to be a ten cent piece, is dropped by a customer into one of the coin drops D. The coin as it drops makes and breaks in the coin drop D a first contact switch, and thereafter makes and breaks a second contact switch, sending successively two current impulses to the solenoid coil I0. Each momentary energization of the coil causes two reciprocations of the armature rod II, which in turn twice makes and breaks engagement of the leaves BI and 65 with the contacts 60 and 63 respectively. At each engagement of the switch leaves with the contacts an alternating current impulse of service voltage and frequency, which we shall assume to be 110 volt and 60 cycles, is sent from the transformer 3! over conductors 82, 83, 84, and 85 to the amplifier RA at an initial level of approximately 12 decibels or less, depending on the length of the cable conductors. The transformer BI is designed to change the voltage from a 110 to 6.3 volts. The amplifier RA receives this 6.3 volts 60-cycle current across 600 ohms at zero, or a low plus-level, and changes the signal impulses thus received by it to approximately 3 watts or 39 volts across a 500 ohm load and trans mits these impulses over an electric circuit consisting of the conductor II 8, the terminal I05, the switch arm IN, the contact I00, the conductor I26, the conductor I20, the electromagnet 205 of the coin indicator I, and the ground return I29 to the ground return I33 of the amplifier RA. In a manner already described, this electromagnet 205 operates the mechanism of the coin indicator I to move the pointer 33 to position 2 on the dial 32, at the same time illuminating the lamp 34.

The operator notified by the illumination of the lamp 34 notes the number indicated by the pointer 33, moves the talk-listen-play switch 'ILPS to its extreme right-hand position in which the switch arms IOI, I02, and I03 engage the contacts I06, III), and H4, respectively. Talking into the microphone MI, she asks the customer for identifying numbers or names of the two records which he wishes played. The audio-irequency signals impressed upon the system by her voice are fed into the amplifier SA through an electrical circuit consisting of the conductor I26a, the contact I I4, the switch arm I03, the terminal N3, the conductor I23a, and a ground return. The amplifier SA transmits her voice signals at a maximum of zero level over the conductors I53 and I53 and telephone cable conductors 84 and 85, switch leaves 6! and 65, contacts 62 and 64, conductors TI and III, switch leaves 56 and 50, contacts 55 and 53, conductors I6 and I5, to the amplifier FA, which increases the signals from a minus level, which may be as low as minus decibels to plus decibels, or approximately 6 watts, and transmits them over conductors 89 through the matching transformer MT to the high fidelity speaker HF, from which they are heard by the customer. In this position of the talk-listen-play switch TLPS, the switch arm IOI engages the contact I06. This position of the switch arm l0I makes it possible for an additional coin dropped in the coin drop D to be registered by the pointer 33 by signal impulses traveling over conductors I20 and I29 to the electromagnet I05. Also in this switch position, the arm I02 engages the open contact IIO. It will also be noted that while the operator is talking to the customer, she must hold the switch arms Iol, I02, and I03 in their rightward position against the action of the spring II'I.

As soon as she is through questioning the customer, she allows the spring III to return the switch arms IOI, I02, and I03 to their central position in which they engage the contacts I01, III, and H5 respectively. The customer, first pushing in the button 4|, talks into the microphone M, telling the central station operator the records he wishes played. The audio-frequency signals thus impressed upon the system are transmitted through the conductor 86 and ground 81 to the amplifier MA, where they are transformed to a maximum of zero level signals and transmitted over the conductors 13 and I2, the contacts 52 and 58, the switch leaves 50 and 56, the conductors I4 and II, the contacts 64 and 62, the switch leaves 65 and 6|, and conductors and 84, to the amplifier RA, where they are received at a minus level as low as minus 10 decibels and raised to signals of plus 27 decibels and transmitted over the conductor II8, the terminal I05, the switch arm IOI, the contact I01, the conductor I2I, the volume control VCO, the conductors I22, through the matching transformer MTO which has a grounded return to the amplifier, and over the conductors I23 to the speaker 0, where they are heard by the operator. It will be noted that in this position of the switch arm IOI, should any further coin or coins be dropped into the coin drop D, sig nals will be fed into the amplifier MA and, by the same circuit as the customer's audio-frequency signals, transmitted to the ear of the operator as clicks which she will record in writing, crediting the customer with that many additional record playings. It will also be noted that in this position of the talk-listen-play switch TLPS, the

switch arm I02 engages an open contact III and the switch arm I03 engages the contact II5 which is grounded through the conductor I25a to the amplifier SA thereby short circuiting the grid of the input tube in this amplifier while the talk-listen-play switch is in the central or listening position to prevent any signal or stray pickup being amplified thereby.

The customer now releases the push button 4I and the operator returns the talk-listen-play switch TLPS to its leftward position, places the first of the requested records on the turntable of the record reproducing unit, PI, sets the turntable in operation, causing. the recorded sounds in the form of audio-frequency signals to be transmitted through the equalizer E and over the conductor I24a to the contact H6 and thence to the amplifier SA through the switch arm I03, terminal I I3, and conductor I23a, and by ground return to the unit PI and equalizer. These audio-frequency signals when received by the amplifier are changed to signals of zero level maximum and transmitted over conductors I53 and I54, the cable conductors 84 and 85, switch DPR, conductors I1 and I4, switch DPP, and conductors I6 and I5 to the amplifier FA where they are received at a minus level, which may be as low as minus 10 and increased to plus 30 decibels, and sent through the matching transformer MT to the high fidelity speaker HF over conductors 89 and reproduced as sound waves at the location station; It will be noted that in this position of the talk-listen-play switch TLPS, the switch arm IIlI engages the contact I08, enabling the deposit of any additional coin or coins in the coin drop to be registered by the pointer 33. In this switch position the arm I02 engages the contact II2, connects the shunt resistor I22a around the volume control V to lessen the gain for record reproduction as will be explained later.

When the operator is listening to signals issuing from the speaker 0 coming from any one of the three location stations connected thereto, she may regulate the volume level of these signals by manipulation of the volume contra] VCO.

The volume indicator VI may be connected to any one of the three amplifiers SA of a section CS of the cabinet by operation of the volume indicator switch VIS, enabling the operator to reg ulate a zero level maximum the signals leaving the amplifier SA for the high fidelity speaker HF by manipulation of the associated volume controls VC (see diagram of amplifier SA, Fig. 2). For testing the quality of the music reproduced from a record on any one of the playing tables, the operator may connect the monitor speaker, amplifier MSA, and monitor speaker MS to any amplifier SA by means of the monitor speaker switch MSS, which is connected as indicated to each SA amplifier of each control section CS by conductors I99 and 200. The operator thus acquires the informatlon needed for discarding damaged or worn-out records, or for other purposes. I

Fig. shows a wiring diagram of a modified form of the invention. It is in many respects similar to Fig. 2, showing the devices and wiring connections of a location station to the left of the line a:-:v and the devices and wiring connections of aflcontrol' unit C to the right of the line :c-ar. The devices and connections which are shown on Fig. 2, and which also appear on Fig. 10, are given in the latter figure the same designating numerals and characters.

10 will be confined to those respects in which it is different from the Wiring diagram of Fig. 2.

One sideof the electrical circuit through the coin drop D of location station La is connected by conductors I'56and I63 to a cable conductor I68. The other side of the circuit through the coin drop D is connected by a conductor I60 to the low potential coil I6I of a step-down 6.3 volt output transformer I62 the high potential coil of which is connected to an electrical service of, for example, alternating current of 110 volts and SO-cycle frequency, by conductors I64. The other end of the transformer coil I62 is connected by conductors I65 and I66 to the center tap I61 of a hybrid transformer coil 61a of an amplifier FAH which is a triode power amplifier with hybrid transformer. The conductor I69 connects one end of the transformer coil 61a of the amplifier FAH with the cable conductor I10. A conductor I1! connects the other end of the trans former coil 61a with the cable conductor I 68 through a balancing network I12.

One terminal of the coil 66 of the amplifier MA is connected to the cable conductor I68 by conductor I51, a switch leaf of push button switch I58, conductor I51a and conductor I63. Th other terminal of this coil is connected to the center tap it of the hybrid transformer coil 61a of the amplifier FAH by conductor I66 he The following explanation of the wiring diagram shown in Fig.

other switch leaf of push button switch I58, and conductors I66a and I66. The switch leaves of the switch I58 establish this circuit only when the switch button is manually pushed inwardly, but the coin drop is connected to the cable conductor I68 and center tap I61 irrespective of the position of the switch button of the switch I58. A bridging resistor I58a, connecting the switch leaves when the push button is in its outer posi-- tion, provides an impedance in the coin drop circuit equal to that of the circuit connecting the amplifier MA with the central control station CCS.

Provision may be made for bridging the switch I58 by conductors I59 shown in dotted lines on the drawing and so constructed and arranged in the form of any suitable device that the bridging may be made effective or not as desired.

The cable conductor I10 is connected by a conductor I14 to one end of a hybrid transformer coil I13 of a triode line amplifier SAH with hybrid output transformer. The cable conductor I68 is connected by a conductor I16 to the other end of the hybrid transformer coil I13 through a balancing network I15. This cable conductor I68 is also connected to one end of the transformer coil I50 of the amplifier RA by a conductor I11. The other end of the transformer coil I50 is connected to the center tap I18 of the transformer coil I13 of the amplifier SAH by a conductor I18. The coil I13 is a part of a hybrid output transformer I36, the other coil I31 of which is connected to the transformer coil I55 of the amplifier SA by conductors I53 and I54.

These connections provide ahybrid circuit by which cable conductors I68 and I10 serve to transmit signals simultaneously from the amplifier MA or coin drop D to the amplifier RA and from amplifier SAH to amplifier FAH.

The hookup shown to the left of the line :c-x of Fig. 10 may be combined with the hookup shown to the right of the line' :r:c of Fig. 2, providing a semi-hybrid circuit in which the network I'12 of all stations may be given a permanent balancing adjustment at the factory.

When the bridging connection I59 is not installed, or when, if installed, it is made inoperative, the push button switch I58 must be closed by the customer when he desires to talk to the central station operator. In all respects insofar as the human element is concerned, the operation of the system of which the wiring diagram is shown in Fig. 10 is the same as that ofthe system the wiring diagram of which is shown in Fig. 2, it being understood that the push button operated by the customer is in the one case that designated I58 on Fig. 10, and in the other case that designated 4| on Fig. 2. It will also be understood that in the case of the system shown in Fig. 10, only two electrical connections must be made at the location station to prepare the system for operation, i. e., the conductors 88 of the power supply unit PS and the conductors I0 3 of the coin drop transformer coil I62, whereas in the system shown in Fig. 2, electrical connections to a current source must be made for.

the conductors 88 of the power supply unit PS, the conductors 68 and 65 of the coin drop D, and the conductors of the relay circuit of the coin drop D.

As has been stated at the beginning of this description of the invention, one of the objects is to provide a system so equipped that the different types of signals such as coin drop, vocal and record signals, will be transmitted without mutual interference or confusion, over a single telephonic circuit. This is accomplished in the system of this invention by either preventing simultaneous transmission of signals of different types or providing for non-interference between simultaneously transmitted signals. Some of the means for accomplishing this general object will be cited.

Since the talk-back amplifier MA, if it were not for the push button switch I58, would be connected to the central control station CCS in parallel with the amplifier FAH at all times, although in this hybrid circuit the attenuation between the two amplifiers MA and FAH is approximately 20db, when enough volume to properly transmit signals from amplifier MA to amplifier RA is allowed, there would result a feedback between the microphone M and the high fidelity receiving speaker HF causing a slight distortion in the reproduction of a record which may be being played at the same time. The push button I58 also eliminates any chance of conversation held in the neighborhood of the microphone M from being accidentally transmitted back over the telephone lines to the central con- ..trol station to the confusion of the operator.

In the hookup shown in Fig. 2, the switch DPP accomplishes the same purpose as switch I58 in the hybrid circuit hookup, disconnecting the amplifier FA altogether from thetelephone lines while the customer is speaker into microphone M, and normally disconnecting th amplifier and microphone M.

The D. P. R. relay switch is used in the hookup shown in Fig. 2 because otherwise the coin drop 60 cycle signals, which are transmitted at approximately plus 12 decibels, would enter the amplifier FA with the result that since it is designed to receive not stronger than zero level signals a very loud buzz would be heard from the speaker HF with every coin signal.

Instead of using a combined speaker and microphone at the central control station or the location stations, a microphone MI and a separate speaker O are used at the central control station and a microphone M and separate speaker HF are used at the location stations with individual one-way amplifiers. This makes it possible to use a relatively expensive high fidelity speaker HF and associated amplifiers SA and FA to faithfully transmit the record reproduced sounds with sound-level equalization from 50 to 6000 cycles, and relatively inexpensive 5 inch speakers for the mic ophone M and the speaker O. This also avoids the use of two-way amplifiers which cannot be designed for faithful amplification. If the speaker were switched to the SA, FA, HF circuit for talking by the operator to the customer, the speaker HF would reproduce her words in a boomy" manner, whereas by using a separate microphone MI correctly designed solely for sound wave reception, good clear speech tones are transmitted over the high fidelity circuit SA, FA, HF. The microphone M is preferably a inch speaker and the amplifier MA is designed to cut ofi all "frequency from 50 to 1000 cycles, giving crispness of speech at the speaker O.

The coin indicator I is provided with an actuating coil so associated with a condenser as to confine its responsive energization toa definite frequency. i. e., that of the service power supply, because the signal impulse which must be indicated to the operator comes over conductors in a telephone utility's cable. These utilities stringently limit both the amperage and the voltage of the current which they will permit lessees to put through their cable conductors that there may be no cross signalling between cable circuits. Such a limitation is, for example, .to 350 milliamps as to current fiow and 120 volts as to current potential. They also forbid the use of direct current. Under these limitations it becomes impossible to energize the electromagnet of a mechanical signalling device by such weak signals without using one or a. series of auxiliary circuit closing relays, the relay first receiving the current from the telephone cable conductors having obviously to be of delicate and expensive construction and at best being uncertain in its operation. Even though direct current were permitted through the cable conductors auxiliary circuit, closing relays would still be necessary.

If A. C. signals are to be increased in strength by vacuum tube amplification, the usual untuned electromagnet if used in the signalling device, will be operated by the audio-frequency signals which come through the cable conductors in a system of the kind which is the subject of this invention unless the prohibitively expensive expedient be adopted of providing a separate telephone cable circuit for coin signalling; for it must be remembered that in a single cable circuit system, coin signals and audio-frequency signals cannot be segregated by switch means at the central control station but all are impressed on the central station devices through permanent connections. In a system constructed in accordance with this invention, the electromagnet is tuned to operate only at the utility service frequency which is below audio-frequency, and the same receiving amplifier which builds up and sends on the audio-frequency signals of the customer to the operators speaker also performs the same function for the coin signals on their way to the electromagnet of the coin indicator. 60- cycle signals operate the indicator and are heard out of the speaker as clicks. Signals of higher frequency operate only the operator's speaker. The equipment is simple, inexpensive and certain in its operation. The tuned electromagnet is in operative principle a speaker responsive to signals within a narrow frequency band and functioning to turn a Geneva movement instead of to vibrate a speaker diaphragm.

Since the microphone MI requires more gain than the phonograph pickup, the shunt resistor M211 is connected across the volume control VC of the amplifier SA by the switch arm 12 when switch arm I03 is positioned to connect the record playing reproducer PI with the amplifier SA in order to reduce automatically, without manual adjustment of a volume control, the gain of the amplifier for record reproduced signals from that which characterizes it when used to amplify vocal signals from the microphone.

As previously stated one of the objects of the invention is to properly regulate the intensity levels of the signals of the several types at the several places of the system. Some features of these regulating means will be pointed out. The

basic regulation is of course accomplished in the design of the amplifiers themselves and the provision of impedance devices supplementary to the impedance of system elements required primarily for other functions. Since, however, the frequency-intensity ratio of alternating current varies with the frequency when transmitted over telephone cable lines and some of the other parts of the equipment of a system of the type described,

- and since the records themselves are made by current characterized by such a variable frequency-intensity ratio and reproduce in the same fashion, and since the phenomenon of frequencyintensity variation may be effectively used to further the object of eliminating interference between signals of different types, the invention contemplates the use of filters for regulating to desired characteristics the frequency-intensity curve at various points in the signal circuits.

The telephone utilities limit the decibel gain from the input to the output of any amplifier connected to their lines over the most heavily used audio-frequency range to protect their cable circuits from improper operation. A typical requirement is that the gain be no more than 30 db. at 1000 cycles per second. But this gain is not quite enough power to drive the system efliciently in a large room. We therefore design the FA amplifier with an overall gain of 36 db. and use with it the dipper filter DF which decreases the intensity, beginningat 500 cycles, to a 6 db. maximum drop from 36 to 30 at 1000 cycles and then increases it to 36 db. at 1500 cycles. Thereby a greater intensity is secured for most of the audiofrequency range of record-reproduced signals, and the intensity drop of 6 db. at 1000 cycles does not noticeably affect the character of the reproduction.

Assuming that, whatever the frequency-intensity curve of the record-reproduced signals, the record reproducing unit PL and the equalizer E are designed to feed signals into the amplifier SA substantially flat for all frequencies, and since the electromagnet 205 of the coin signalling device I operates on a signal coming into the amplifier RA at approximately zero level, it is necessary that signals from the reproducing unit at 60 cycles and frequencies in that low band leave the amplifier SA at low intensity. which tests show should be not more than a minus ten db. level. Therefore, the amplifier SA is provided with the cutoif filter EQC designed to begin to attenuate signals at 100 cycles with a maximum attenuation of about db. at 50 cycles. Since in the telephone cable conductors between amplifier SA and amplifier FA, there is always a gain on low frequencies due to inherent characteristics oi the telephone systems equipment, this attenuation brought about by the filter EQC serves the double purpose of preventing accidental tripping of the coin indicator L and of flattening the frequencyintensity curve of the signals coming into the speaker HF.

It will thus be seen that according to this invention signals from the record reproducing unit PI are flat down to 100 cycles as they leave the amplifier SA. As a matter of fact due to a slight gain between 100 and 75 cycles of the signals as they enter the equalizer EQC due to the character of the frequency-intensity curve of the record itself and the equalizing action of the equalizer E, the signals from the record-reproducing unit are fiat to 75 cycles as they leave the amplifier SA. But the signals from the record reproducing unit PI between 75 and 150 cycles might chatter or trip the coin indicator if they at times come into the amplifierRA at above zero level, even though the indicator mechanism is tuned to 60 cycles. To guard against this contingency, a 100 cycle dipper filter EQD is incorporated in the amplifier RA which begins attenuation at 60, reaches a maximum of minus 18 db. at 100 and reaches zero attenuation again at about 150 cycles. The filters EQC and EQD cooperate to prevent accldental operation of the coin indicator by audiofrequency signals emanating from either the location station L or the central control station CCS. If EQC were designed to provide a safety attenuation for the coin indicator at cycles, the quality of the reproduction at HF would be impaired. If the filter EQD attenuated below 60 cycles, the coin drop signals would not trip the coin indicator.

It is clear that some features of this invention can be used independently of others and that the invention is capable of a variety of embodiments. The invention is not tobe limited to any specific embodiment but is defined in the following claims.

In the claims, the term microphone is used to refer to a device of which the function is to convert air sound waves into electric undulations of corresponding frequency and amplitude. The term speaker" is used to refer to a device of which the function is to convert electric undulations into air sound waves of corresponding fre quency and amplitude.

We claim as our invention:

1. In a record-playing system of the character described for use in a two-conductor telephone circuit, the combination of z a first microphone; a first one-way amplifier connected to receive and amplify signals from said first microphone and connected to one end of said circuit for transmission of said signals thereover; a first speaker a second one-way amplifier connected for reception and amplification of signals from said one end of said telephone circuit and transmission of said signals to said speaker, said microphone, speaker and amplifiers being grouped at a location station; a third one-way receiving amplifier connected to the other end of said circuit; a fourth one-way receiving amplifier connected to said other end of said circuit; a speaker connected to the out-put end of said third amplifier; and a sound-record-reproclucing means connected to the input end of said fourth amplifier.

2. In a record-playing system of the character described, the combination with a single two-conductortelephone circuit of a first microphone; a first one-way amplifier connected to receive and amplify signals from said first microphone and connected to one end of said telephone cir-- cuit to transmit signals thereover; a first speaker; a second one-way amplifier connected to receive and amplify signals from said one end of said telephone circuit and transmit them to said first speaker; a coin drop connected to said one end of said circuit to transmit signals thereover, said first microphone, first speaker, coin drop, and first and second amplifiers being grouped at a location station; a second microphone; a record-reproducing unit; a third one-way amplifier connected to receive and amplify signals from said second microphone and said record-reproducing unit and connected to the other end of said circuit to transmit signals thereover; a second speaker; a coin indicator; and a fourth one-way amplifier connected to receive and amplify signals from said other end of said circuit and transmit them to said second speaker and said indicator, said sec ond' microphone, record-reproducing unit, second speaker, coin indicator and third and fourth amplifiers being grouped at a central control station.

3. In a remote control record playing system of the character described for transmitting sound over a plurality of two-conductor telephone circuits, the combination of: a plurality of separate location stations; means for operatively connecting each of said location stations to one end of a corresponding one of said telephone'circuits; a central control station at the other end of said telephone circuits, said control station including a microphone, a sound reproducing means, and means for connecting said microphone and said sound reproducing means selectively to said telephone circuits; a coin operated switch at each location station for transmitting an electric impulse over the electric circuit associated with this said station; an indicating means at said control station for each of said circuits for indicating the number of actuations of said coin-actuated switch by current flowing over the corresponding telephone circuit; and a plurality of record-playing means at said control station corresponding in number to said circuits and said location stations and respectively associated with them for transmitting over any particular circuit a number of received by said indicating means.

4. In combination with a telephone circuit: means for transmitting over said circuit electric impulses of varying frequency corresponding to sound undulations; an impulse switch connected to one end of said telephone circuit and adapted when momentarily closed to deliver to said telephone circuit an alternating potential of constant frequency; and indicating means adapted to be connected to the other end of said telephone circuit to receive both said electric impulses corresponding to sound undulations and said alternating potential of constant frequency, said indicating means including means selectively actuatable by said alternating potential of constant frequency.

5. In combination with a telephone circuit including not more than two conductors: a first sound reproducing means; a first microphone; means for selectively connecting said first sound reproducing means and said first microphone to records corresponding to the number of impulses one end of said circuit; a second sound reproducing means; a second microphone; means for selectively connecting said second sound reproducing means and said second microphone to the other end of said circuit; an indicating means at one end of said circuit tuned to operate at a given frequency; and means connectible to the opposite end of said circuit to impress thereon said given frequency to actuate said indicating means.

6. A combination as defined in claim 2, including a sound record reproducing means and means for connecting same to that end of said circuit to which said indicating means is connected.

7. In a record-playing system of the character described for use with a two-conductor telephone circuit, the combination of: means connected to one end of said circuit at a location station for translating waves of varying frequency from an electrical conductor medium to an air medium, and from an air medium to anelectrical conductor medium; means at said location station for impressing on said one end of said circuit electrical impulses of a definite constant frequency; means at a central control station at the other end of said circuit for translating waves of varying frequency from an electrical conductor medium to an air medium, and from an air medium to an electrical conductor medium; means at said control station for selectively receiving and indicating said electrical impulses of a definite constant frequency; and means for reproducing a sound record at said central station, said means being connected to said other end of said circuit.

8. In a record-playing system of the character amplifying them; a plurality of second separate described for use with a single two-conductor telephone circuit, the combination of: a location station comprising means connected to one end of said circuit for translation of waves of variable frequency from an electrical conductor medium to an air medium, and from an air medium to an electrical conductor medium, and further comprising means for impressing indicative signalling impulses of unvarying character on said circuit; a receiving indicator at a central control station connected to the other end of said circuit and adapted to selectively receive said impulses of unvarying character; a record reproducing means at said central control station; a first means at said central control station for receiving from said other end of said circuit, and amplifying electrical undulations; a second separate means at said central control station for implifying and transmitting to said other end of said circuit electrical undulations; a sound speaker at said central station responsive to said signalling impulses of unvarying character; a microphone at said central station; and a switch mechanism at said central station adapted to assume three positions, in the first position of which said switch connects said record reproducing means with said second amplifying means and connects said first amplifying means with said receiving indicator, inthe second position of which it connects said first amplifying means with said speaker, and in the third position of which it connects said microphone with said second amplifying means and connects said first amplifying means with said receiving indicator.

9. In a record-playing system of the character described for use with a plurality of two-conductor telephone circuits, the combination of: a plurality of location stations, each comprising means connected to one end of an associated one of said circuits for translation of waves of variable frequency from an electrical conductor medium to an air medium, and from an air medium to an electrical conductor medium, and further comprising means for impressing indicative signalling impulses of unvarying character on said circuits; a plurality of receiving indicators at a central control station at the other'end of said circuit, each associated with one of said circuits and adapted to selectively receive impulses of said unvarying character; a plurality of recordreproducing means at said central control station, each associated with one of said circuits; a plurality of first means at said central control station, each for receiving from an associated one of said circuits electrical undulations and means at said central control station for amplifying and transmitting over an associated one of said circuits electrical undulations; a sound speaker at said central control station responsive to said signalling impulses of unvarying character; a microphone at said central station; and a plurality of switch mechanisms at said central station, each corresponding to one of said circuits and each adapted to assume three positions, in the first position of which said switch connects its record-reproducing means with its second amplifying means and its first amplifying means with its receiving indicator, in the second position of which it connects its first amplifying means with said speaker,'and in the third position of which it connects said microphone with its second amplifying means and its first amplifying means with its receiving indicator,

10. In combination with a telephone circuit: means for transmitting over said circuit electric impulses corresponding to sound undulations; means for superimposing on said electric impulses an alternating potential of constant frequency, said means including an impulse switch connected to one end of said telephone circuit; an impulse-receiving means connectible to the other end of said circuit in a manner to receive both said electric impulses corresponding to sound undulations and said superimposed alternating potential of constant frequency; and a;

band-pass filter means connected ahead of said impulse-receiving means for filtering therefrom frequencies other than those substantially corresponding to said alternating potential.

11. A combination as defined in claim 10, including an additional filter means ahead of said impulse-receiving means for filtering therefrom a band of frequencies adjacent and greater than said commercial frequency.

12. In combination with a telephone circuit: means connectible to one end of said circuit for transmitting therealong electric impulses corresponding to sound undulations: an impulse-receiving means also connectible to said one end of said circuit and selectively tuned to operate at a given commercial low frequency; means at said one end of said circuit and associated with said transmitting means for substantially attenuating the electric impulses corresponding to sound undulations of said commercial low frequency and those frequencies approximating said commercial frequency whereby said electric impulses corresponding to said sound undulations will not operate said impulse-receiving meansr and means connectible to the other end of said circuit for impressing thereupon said commercial frequency to actuate said impulse-receiving means.

13. A combination as defined in claim 12, including a sound reproducing means at said other end of said circuit, said telephone circuit having means for building up between the ends thereof the amplitudeof low frequencies including said commercial low frequency. 7

14. In a record-playing system of the character described, the combination with a single twoconductor telephone circuit of a microphone; a receiving amplifier for said microphone constructed to substantially cut oil signals of relatively low frequency, and connected to transmit signals above said low frequency range to one end of said telephone circuit; a coin-controlled signalling device connected to said end of said telephone circuit and adapted to impress thereon alternating current signals of a constant frequency within the limits of said relatively low frequency; a speaker connected to the other end of said telephone circuit; a signal indicator connected to said other end of said telephone circuit selectively and exclusively responsive to said signals of constant frequency; means connected to said other end of said circuit for translating sound records and sound into electric undulations; and means at said one end of said circuit for reproducing said undulations as sound.

15. In combination with a telephone circuit including not more than two conductors: afirst sound reproducing means; a first microphone: a spring retrieved two-position push-button switch adapted to connect said first sound reproducing means to one end of said telephone circuit when in normal position and to connect said microphone to said one end of said telephone circuit when in push position; means for connecting a source of alternating current of constant frequency to said one end of said circuit,

said means comprising a switch operable by coin drop for momentarily interrupting said con nections 'between said push-button switch an said one end of said telephone circuit and durin said interruption connecting said alternating cur rent of constant frequency to said one end of sai telephone circuit; a second microphone; a secon sound reproducing means; a sound record repro ducing :means; means for connecting said secon microphone, said second sound reproducin .means and sound record reproducing means i:

the other end of said telephone circuit; and a indicating means connected to said other end c said circuit and tuned to operate at said con stant frequency.

16. In combination with a telephone circuit in eluding not more than two conductors: a two way hybrid telephone system connected to th 'ends of said circuit for transmitting variable and switch; 1 and an impulse signal, receivin device at the other end of said circuit from sai impulse sending means and tuned to respon to signals of said constant frequency.

17. In a tractive electromasnet. the combina tion of: an electromagnetic coil: an armatur member movable in response to the energizatio: of said coil; and impedance means, said imped ance means and said coil being connected t constitute a frequency filter for said coil.

18. In a tractive electromagnet, the combina tion of: an electromagnetic coil adapted for con nection across a circuit of alternating current a condenserconnected in parallel with said co and adapted in conjunction with said coil i selectively pass through said coil alternating cur rent within a predetermined frequency band an reject current of other frequencies; and an a: mature member movable in response to the cue: gization of said coil;

19. In an indicating device, the combination 01 a tractive electromagnet; a Geneva movemer star wheel; a stop fixing the initial position i said star wheel; an indicating arm mounted i move in correspondence with said star whee a Geneva movement pawl mechanism engagin said star wheel; a movable armature for tr electromagnet connected to operate said paw mechanism to cause movement of said star who from said initial position: a make-and-bres switch adapted to be open when said star whei is in said initial position and closed when sai star wheel is in other than initial position; a incandescent lamp; and electrical conductoi connecting said lamp in series with the termina of said switch and with a source of current.

20. In a sectional unit of a multiple unit cor trol cabinet for remote control record-playin system, the combination of: a plurality of ve: tically spaced horizontal shelves of substantial equal width, each projecting forwardly part we over the next lower shelf to form a hood there over; a record turntable and reproducing un mounted upon each shelf; a vertical panel e1 tending upward from the rear edge of the uppermost shelf; control and indicating devices associated with the operation of said turntables and reproducing units' on said panel: and a frame structure supporting said shelves and panel and providing below said shelves a protecting housing for control and operating mechanism associated with said turntables and reproducing units, each said sectional unit being adapted for lateral securement to another said sectional unit.

21. In combination with a telephone circuit including not more than two conductors: a twoway hybrid telephone system connected to the ends of said circuit for transmitting variablefrequency alternating current in both directions over said circuit comprising a first receiving amplifier with a. hybrid transformer and a first sending amplifier and further comprising a s1 ond receiving amplifier and second sending a1 piifler which is connected to the same end of i telephone circuit as said first receiving amplifl said connection on one side being through a ce ter tap of the said hybrid transformer; a tu pole switch for disconnecting said second sen ing amplifier from said circuit connection; mea for sending alternating current impulse sign of constant frequency connected to said circi in' parallel with said switch; and an impulse si nal receiving device at the other end of said c1 cult from said impulse sending means and tun to respond to signals of said constant frequent FRED A, HADEL. REA J. THOMPSON CERTIFICATE OF CORRECTION. Patent No. 2,;58,976. April 22, 19in.

FRED A. HADEL, ET AL. It is-h ereb y certizfied that error appears in the above numbered pate: requiring correction as follows: In the grant, lines 2and5, for "assigno:

of one-half to CARL F. HU'EBOTIER, of Los Angeles, California" read --assi ors,by direct andmesne assignments, of one-half to CARL F. HU'EBOTTER, Los angeles, California, and one-half to said-HADEL, and line 13, r: "Fred A. Hadel and Rea- J. Thompson, their heirs" read -Fred-A. Hadel a1 Carl 'F. Huebotter, their heirs-; in the heading to-the printed specific:

tion-,'lines 5and 6, for "assignors of one-half to Carl F. Huebotter, Lc

Angeles, Calif." read assign0rs, by direct and mesne assignments, of, or .half to Carl F. Huebotter, Los Angeles, Calif. and one-half to said Hadelas shown by the record of assignments in this .office; page 5, first colun line 65, for the word "proper" read upper--; page 7, first column, line 1 for Peontral read -c'ontrol-; page 8 first column, line 51, for the we "speaker" read "s eaki and that the said Letters Patent should 1 read with this correction therein that the same may conform to the race of the case in the Patent Office.

Signed and sealed this 5rd day-of June, A. D. 19LL1 V, g Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

